Answer:
Ammonia and Hydrogen Chloride.
Explanation:
Assuming this is what you're referring to, Ammonia (NH3) and Hydrogen Chloride(NCI3). The concentrated ammonia (NH3) is placed on a pad in one end of a tube and hydrochloric acid (NCI3) on a pad at the other. Shortly after the gases will begin diffusing far enough to meet, a ring of solid ammonium chloride (NH4Cl) will be formed.
